1. Field of the Invention
The present invention relates to an ultrasonic probe.
2. Description of the Related Art
To reduce the side lobe of the sound field in a lens direction and achieve a uniform sound field, in an ultrasonic probe, a technique weights the transmission sound pressure intensity and the reception sensitivity. Examples of this technique include a method of forming grooves in a piezoelectric element which extend from the center to the end in the lens direction to gradually decrease the area of the piezoelectric element. In this case, these grooves may or may not divide the piezoelectric element completely. According to this method, only a resin material such as an epoxy resin fills the grooves of the piezoelectric element. This, however, leads to a composite structure in which the coefficient of thermal expansion of the grooves filled with the resin is different from that of the piezoelectric element. Hence, when the temperature changes in the piezoelectric element between the time when it is stored and the time when it generates heat, the degree of expansion differs between the grooves filled with the resin and the piezoelectric element. Then, a stress or strain occurs in the piezoelectric element, degrading the mechanical reliability. Due to the viscosity of the resin, the cutting load increases when cutting the piezoelectric element in an array direction, and the piezoelectric element easily breaks. Consequently, the yield of the piezoelectric element is reduced.